1. Field
The present invention generally relates to drilling tools that may be used to drill geological and/or manmade formations and to methods of manufacturing and using such drilling tools.
2. Technical Background
Drill bits and other boring tools are often used to drill holes in rock and other formations for exploration or other purposes. One type of drill bit used for such operations is an impregnated drill bit. Impregnated drill bits include a cutting portion or crown that may be formed of a matrix that contains a powdered hard particulate material, such as tungsten carbide. The hard particulate material may be sintered and/or infiltrated with a binder, such as a copper alloy. Furthermore, the cutting portion of impregnated drill bits may also be impregnated with an abrasive cutting media, such as natural or synthetic diamonds.
During drilling operations, the abrasive cutting media is gradually exposed as the supporting matrix material is worn away. The continuous exposure of new abrasive cutting media by wear of the supporting matrix forming the cutting portion can help provide a continually sharp cutting surface. Impregnated drilling tools may continue to cut efficiently until the cutting portion of the tool is consumed. Once the cutting portion of the tool is consumed, the tool becomes dull and typically requires replacement.
Impregnated drill bits, and most other types of drilling tools, usually require the use of drilling fluid or air during drilling operations. Typically, drilling fluid or air is pumped from the surface through the drill string and across the bit face. The drilling fluid may then return to the surface through a gap between the drill string and the bore-hole wall. Alternatively, the drilling fluid may be pumped down the annulus formed between the drill string and the formation, across the bit face and return through the drill string. Drilling fluid can serve several important functions including flushing cuttings up and out of the bore hole, clearing cuttings from the bit face so that the abrasive cutting media cause excessive bit wear, lubricating and cooling the bit face during drilling, and reducing the friction of the rotating drill string.
To aid in directing drilling fluid across the bit face, drill bits will often include waterways or passages near the cutting face that pass through the drill bit from the inside diameter to the outside diameter. Thus, waterways can aid in both cooling the bit face and flushing cuttings away. Unfortunately, when drilling in broken and abrasive formations, or at high penetration rates, debris can clog the waterways, thereby impeding the flow of drilling fluid. The decrease in drilling fluid traveling from the inside to the outside of the drill bit may cause insufficient removal of cuttings, uneven wear of the drill bit, generation of large frictional forces, burning of the drill bit, or other problems that may eventually lead to failure of the drill bit. Furthermore, frequently in broken and abrasive ground conditions, loose material does not feed smoothly into the drill string or core barrel.
Current solutions employed to reduce clogging of waterways include increasing the depth of the waterways, increasing the width of the waterways, and radially tapering the sides of the waterways so the width of the waterways increase as they extend from the inside diameter to the outside diameter of the drill bit. While each of these methods may reduce clogging and increase flushing to some extent, they also each present various drawbacks to one level or another.
For example, deeper waterways may decrease the strength of the drill bit, reduce the velocity of the drilling fluid at the waterway entrance, and therefore, the flushing capabilities of the drilling fluid, and increase manufacturing costs due to the additional machining involved in cutting the waterways into the blank of the drill bit. Wider waterways may reduce the cutting surface of the bit face, and therefore, reduce the drilling performance of the drill bit and reduce the velocity of the drilling fluid at the waterway entrance. Similarly, radially tapered waterways may reduce the cutting surface of the bit face and reduce the velocity of the drilling fluid at the waterway entrance.
One will appreciate that many of the current solutions may remove a greater percentage of material from the inside diameter of the drill bit than the outside diameter of the drill bit in creating waterways. The reduced bit body volume at the inside diameter may result in premature wear of the drill bit at the inside diameter. Such premature wear can cause drill bit failure and increase drilling costs by requiring more frequent replacement of the drill bit.
The lack of water on the cutting surfaces of conventional drill bits results in a decrease in the rate at which cuttings are removed, thereby leading to an increase in the wear of the cutting surface. Additionally, the lack of water flow can also minimize the removal of heat from the cutting surface during high-rotational operation of the bit. These known drill bit designs are also associated with relatively low penetration rates and reduced contact stress measurements.
Accordingly, there are a number of disadvantages in conventional waterways that can be addressed. In particular, there is a need in the pertinent art for drill bits that more effectively provide high velocity fluid flow to the cutting surface of the bit and remove heat from the cutting surface. There is a further need in the pertinent art for drill bits that provide increased cutting removal rates and penetration rates in comparison to conventional drill bits.